Diabetes Insipidus as Initial Presentation of Rathke＇s Cleft Cyst

To the Editor： A 56-year-old Chinese man was referred to Peking Union Medical College Hospital because of polydipsia （9000 ml/24 h） and polyuria （7000 ml/24 h） for over 20 days accompanied with intermittent moderate headache in frontal and temporal areas of both sides for about 2 weeks. The patient underwent a brain magnetic resonance imaging （MRI） with contrast in a local healthy facility, revealing that there was an irregular pituitary lesion measuring 1.1 cm× 1.4 cm× 2.2 cm. Apparently, the diagnosis of central diabetes insipidus （DI） was made, but the pituitary lesion remained to be elucidated. The patient received desmopressin acetate tablets （1.2 mg, q.n.） to ameliorate polydipsia （5000 ml/24 h） and polyuria （4000 ml/24 h）.